Before the break-up of the Bell System in the early 1980's, telecommunications line and equipment testing was relatively easy, because a single entity was usually responsible for providing end-to-end service to telephone customers. After the break-up, the situation changed: it became necessary to isolate the source of the problem in order to identify the entity responsible for repairing "troubles" in a customer's telecommunications service. This is true because several entities are now responsible for providing individual portions of the end-to-end service that was previously supplied by a single carrier. In particular, Customer Premises Equipment (CPE) such as station equipment and private branch exchanges (PBX's) are now usually the customer's responsibility. The local loop between CPE and the Central Office is typically the responsibility of the Local Exchange Carrier (LEC), while long distance facilities are usually the responsibility of an Interexchange Carrier (IXC) such as AT&T.
The process of isolating a problem arising in CPE as opposed to in the network (or vice versa), often involved dispatching a craftsperson or technician to the customer's premises with test equipment that could be plugged into the line and locally activated, so as to isolate the defect as either on the network side or the CPE side. See, for example, U.S. Pat. No. 4879739, entitled Wiring Test Device and Method, issued Nov. 7, 1989 to Henry M. Forson, which describes test equipment having two parts: a battery powered, hand-held signal generator adapted to be connected to a home or business telephone line at the interface between the telephone company wiring and the home or business wiring, and a hand-held receiver adapted to be plugged into each modular telephone jack of the home or business line. The signal generator successively applies a uniquely coded pulsed signal to each wire of the line, and monitors the results obtained, in order to isolate the problem to either the home/business line or CPE, on the one hand, or the telephone company line, on the other hand. A visual indicator such as an LED in the receiver indicates reception of the applied test signals. Reception of the wrong signal on a given line indicates a possible cross connection; reception of the same signal on more than one line indicates a short between the lines, and failure to receive any signal on a line indicates an open (break).
The Forson approach was complicated, because two pieces of apparatus were involved in the testing procedure, and inefficient, because testing still had to be done locally, by a craftsperson or technician, at the customer premises. These difficulties were somewhat alleviated in other arrangements, which provide a remotely actuatable testing capability directly at a Maintenance Termination Unit (MTU) typically provided in a jack located at the demarcation point between the telecommunications network and Customer Premises Equipment (CPE). A performance specification for one implementation of an MTU is contained in Bellcore Technical Reference TR-TSY-000324, Issue 1, dated December 1988. Several patents describe MTU-like apparatus for testing telephone lines including: U.S. Pat. No. 4827498, entitled Telephone Line and Instrument Tester, issued May 2, 1989 to James W. Ross; U.S. Pat. No. 4620070, entitled Telephone Line Tester, issued Nov. 28, 1986 to William E. Ruehl; U.S. Pat. No. 4614844, entitled Telephone Service Checking Terminal, issued Sep. 30, 1986 to Budd E. Leeper; and U.S. Pat. No. 4488011, entitled On-Premise Telephone Test Jack, issued Dec. 11, 1984 to M. Mattrice Rogers.
Despite the advances in the design of MTU's, it has nevertheless remained difficult to efficiently identify and isolate troubles that may occur in either the network or the customer's drop and CPE. Some difficulties are associated with the difficulty in using presently available MTU's and similar equipment. Other difficulties are associated with a lack of functionality in such devices.